I bought a new pair of boots ( SIZE 9 1/2 ). My regular size is SIZE 9. The attendant ( boot fitter ) at the ski shop said that it doesn't make any difference. He said: "You are talking a difference of millimeters...".
They fill very comfortable and also have the flex factor ( 100 ) i wanted for my level of skiing. The boots are "dalbellos boss".
I'm not too sure if I made the right decision... I always had SIZE 9.
Going Back to my question. Do millimeters make a difference ?